The reliability of digital circuitry, such as that used in computer data systems, is dependent upon the consistency of its input power. Power outages of even a few milliseconds can cause errors in data, particularly when the line voltage is low and the outage occurs just prior to the sinewave peak.
Numerouse backup power systems have been developed in an attempt to solve this problem. Most such systems use circuitry that switches too slowly between normal and backup operation to safeguard the computer data adequately. Others do not provide digital status signals or allow computer control of the alternate power system.